Photoelectric speed control



March 1953 w. [.BENDZ 2,632,855

PHOTOELECTRIC SPEED CONTROL Filed Oct. 7, 1947 WITNESSES: INVENTOR I 54%? Wa/aemarlfienaz.

ATT RNEY Patented Mar. 24, 1953 PHOTOELEOTRIC SPEED CONTROL Waldemar I. Bendz, Weston, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 7, 1947, Serial No. 778,366

4 Claims. (01. 250-209) My invention relates to electronic speed regulating systems for correlating the travel of web or sheet material to the operation of mechanism, such as printing, or folding machinery.

It is an object of my invention to provide a photoelectric speed control of greatly increased sensitivity and reliability so as to permit, for instance, the use of control marks of less contrasting color or shade relative to the web back-- of a transparent or translucent web so that one u tube reacts to light reflected from marks on the web while the other tube reacts to light passing through the same marks, and I connect the two tubes to an electronic relay system so that the reflectivity and transparency controlled effects acts cumulatively on the same relay equipment to jointly control the associated machinery. As a result, the speed control system is considerably more sensitive to the presence or absence of the control marks within the illuminated zone so that marks which are not discernible to the conventional systems, reacting only on reflected light or only on transmitted light, are readily scanned and responded thereto.

' According to another feature of the invention, I connect the two photoelectric tubes to two respective electronic amplifiers whose output circuits are interconnected by series-connected respective resistors whose common terminal is attached to a capacitive impedance arrangement in the grid circuit of a gaseous discharge relay so that the two photoelectric tubes simultaneously produce two voltage drops across the respective resistors that act cumulatively on the relay trigger circuit.

Systems according to the invention are especially suitable for packaging or cutting machines operating with semi-transparent web material which is commonly used for many products such as candy bars or chewing gum. Hence, an embodiment of a control system according to the invention for such a machine will hereinafter be described in detail although the invention is not limited to this particular kind of machinery. In the drawing; in which an embodiment of my invention is illustrated by its electric circuit diagram and a schematic showing of the controlled regulating mechanisms, the traveling web is denoted by l and one of its printed marks by 2. An optical device for concentrating a beamof light on the mark comprises a lamp 3, operated from a suitable power source such as a battery i, and a lens or system of lenses 5. The direction of web travel is denoted by an arrow D. Two phototubes PI and P2 are disposed at opposite sides of the web so that tube PI reacts to light reflected by the mark 2, while tube P2 reacts to light transmitted through the mark 2.

Tube PI is connected to the input circuit of an amplifier tube Al, and tube P2 is similarly connected to an amplifier tube A2. The output of both amplifiers is combined to control the performance of an electronic trigger relay R which in turn controls motor-driven machinery M that regulates the web travel.

More in detail, the phototube Pl with its lightsensitive cathode l and its anode 8 is coupled to the grid [5 of the amplifier tube Al. Tube Al is shown as a triode, although a pentode is preferably employed to obtain a higher degree of amplification. The coupling of phototube Pl to the grid of amplifier tube Al is through a capacitor I! and resistors l0 and I2. This circuit is conventionally known as impulse coupling of the phototube and responds only to a rapid change in the degree of illumination falling upon the cathode l of phototube Pl. Cathode [4 of amplifier Al is energized by a suitable source such as battery ii. The anode l 6 of amplifier Al is energized by a suitable source of potential, such as battery I9, in series with an anode load resistor 20. Potential for the grid l5 of amplifier Al is supplied by a suitable bias from a source, such as battery [8, which is connected to the grid by a grid resistor 12.

The circuit illustrated is for operation by a reference mark 2 darker than the web material so that the illumination of the phototubecathode I is decreased as the reference mark 2 passes under the scanning light beam. The circuit adjustments are such that bias potential 18 causes a normal fiow of anode current E8 passing through the load resistor 29. The flow of anode current produces a voltage across resistor 20 negative at terminal Tl, whose value depends upon the quiescent point of tube operation. With the light beam shining upon the clear web I, cathode I of phototube Al is illuminated, and phototube current, flowing through resistor 40 from the source of potential 9, causes a voltage across resistor it which is positive at terminal T2. The relatively large voltage across resistor l8 and practically zero voltage across resistor {2 causes capacitor i l to become charged with positive potential at terminal T2. As reference mark 2 passes under the scanning beam, the illumination of cathode l is decreased with a consequent rapid reduction of current through resistor IE3. The voltage across resistor it] drops iaccordingly. Capacitor ii is then discharged through resistors ill and E2 in series. The discharging current flowing through resistor it produces a voltage across resistor 52 which has a negative potential at terminal Til. This negative potential is applied to the grid 150i ampli fier tube A! and immediately reduces the anode current of the tube Al. As a result, the voltage across load resistor it is rapidly reduced and terminal Ti of the tube anode circuit becomes more positive than its normal quiescent potential.

Momentarily neglecting the function of the amplifier tube A2 anditscomponents, thepositivepotential or terminal T l is also increased aboveits quiescent potential because of its connection to terminal Tl through resistor 2i. Coupling capacitor 22 is chargedthrough resistor zilbecause of the increasing positivepotential of terminal T l. Current for charging capacitor 33 flows through resistor 23, the cir cult polarity being such as to make terminal T5 of resistor 23 positive relativeto terminal TS.

t. w l e e o ni hat t e m qne t u ed with phototube B2 and amplifier tube A? are arranged to function in I a duplicate manner to that described previously in connection with phototube PI and amplifier tube Al.

In accordance with this similarity, the elements of the circuit associated with tubes P2 and' AQ are denoted by the same reference numerals as the respective elements (l to ii) of the circuits for-tubes Pi and Al except that the prefix l or IE3 is added to the numerals for the'circuit elements (Nil to I26) of tubes P2 and A2. Similarly, the terminals Ti I, Ti2 and T l 3 correspond to the above mentioned terminals Tl, T2 and T3, respectively.

areference mark 2 passes under the scan ning beam," illumination of the cathode Hill of phototube P2 is decreased because of the decreased light transmission through web i and 7 reference mark i2. Thus, the potential of the terminal Tls to grid H5 of amplifier tube A2 is made more negative than the quiescent potential, and the anode current of tube A2 is decreased The voltage across load resistor I26 is decreased, and the potential of terminal Til becomes more positive than the quiescent potential. Capacitor 22 is charged by the increasing positive potential at terminal TG and the voltage across resistor 23 is'incr'eased by the action of reference mark 2 passing through the scanning beam together with the response of phototube B2 and its associated components.

Itshould be observed that the voltage across resistor 23 is made more positive at terminal T5 either by the decrease of illumination on cathode l of reflected-light phototube Pl, or by decreasing illumination on the cathode lill of transmitted-light phototube P2,, Although the effect upon phototube Pi is amplified by tube Al, and the effect upon phototube P2 is amplified by tube A2, the output of anode circuits of these two tubes ismixed and coupled to the common capacitor 22 throughthe two coupling resistors El-and I2 I. In this way, the simultaneous effects of transmitted light (to phototube P2) and refiected light (to phototube PI) are mixed and summarized to greatly increase the resultant voltage change across resistor 23. Thus, the magnitude of voltage change across resistor 23 is considerably greater than in the conventional electronic regulating schemes.

As mentioned,"the circuit, illustrated in connection with the phototub es: (such as tube PI and the associated components consisting of re sis'tors l!) and I2, coupling capacitor I I and source of potential 9) is such as to respond to a mark 2 darker than the web material. As will be readily'understoodi by anyone familiar with the art, changes in the circuit connections can be 1 made" so as to cause the electronic circuit to become responsive to the conditions existing wherein themark 2 is lighter than the web material I." That is, the system responds equally well to reference marks which reflect or transmit mere. ght han... he eb material itsslt e ore oi g d eriptione plai hea io e we n h han ed l1um ha on fallin -I i" t the tw phqtqtubes Bi and Pil and the changing voltage across resistor 23 which, assumed a positive polarity at, terminal T4. It will. now, be, shown; that the voltage acrossresistor 23 to control d the packaging or cutting, machinery.

in e eq ire nner-J he at we E e instance a thyratron, hasa cathodeAll, a: grid ll and an anode 42. The cathode isenergized The occurrence of a positive, potential atgrid tere minal T l, instantly results in conuuuon,or;nie tube and fiow oianoide ,current lthrough sole? noid This current flows throughthe contact as are timing selector switch 49' Itbrhetu'te' oath-l ode til. Injthisfway, a current is passed-th rd thesol'enoid whe e jer a register -inarkpasses through the scanning lightfbeaml Although this; invention does not relate. to the a cal rat o of a ack in rl utting machine itself, the, appertaining control elements of, a typical ,machineare represented by way. of example for the purpose of fully explaining the operating characteristics of the control" system. The drive for the machinery may consist an electric motor 5 6. A pinion 5| on the motor shaft meshes with a gear 52 whose shaft saber; l'l'S a pair or gears stand" 55 havingdiff ereiit numbers of teeth. Shaft 53 is axiallyslidable tween wqpositm s: W t has a. I ir:vm osition, ear t imia es wit a a 6 t i e ap e ni att r mama. e." ca ed a base speed. Shaft 51 isfconnected to radars as and 53, which pullthe weo'in theldirection 6f the arrow D, normally ata base rate corres nding to the mentioned base speedof shafttl I When shaft 53 is shiftedout ofnorlnal position, gears Lan 5 a e se ed an se r, thn

meshes with a gear 60 of shaft 51 to drive the feed rolls 58, 59 at a slower rate. r

The flow of current through the solenoid 41 causes it to attract the forked magnet armature 6! against a biasing spring 62. Armature 61 engages a collar 53 on shaft 53 and causes lateral shifting of shaft 62 so as to disengage gears E i and 55, and engage gears 55 and 65. In this manner, the operating speed of shaft 51 is reduced below the normal base speed as long as sol noid all is energized.

A cam 6c on shaft controls the selector switch 49 to cyclically open and close its spring biased contact 33. Hence, the action of switch 49 is correlated with the feeding of web i into the mechanism of the packaging or cutting machine (not shown).

One complete cycle of operation occursas follows. As the light of the scanning beam falls upon the clear web l, thyratron R is non-conducting. No current flows through solenoid 4?. Gears 5 and 55 are engaged and rolls 58 and 59 feed the web 1 at the base speed. As reference mark 2 intercepts the scanning light beam, thyratron It becomes instantly conducting. Current flows through solenoid ll. Shaft 53 is shifted to operate gears 53:": and 38. Rolls 58 and 59- then turn at a lower speed, and the feed rate of web i is reduced. As the wrapping or cutting cycle of the machine progresses, cam 64 releases the spring-opened contact 48 of timing selector switch This interrupts the anode current of thyratron R, which immediately becomes nonconducting, and solenoid 47 is deenergized. Shaft 53 is then returned to its normal position and causes gears 55 and 56 to return rolls 53 and 59 to normal speed.

It will be understood that solenoid il and the gears controlled thereby, constitute a magnetically operated speed-change system, which, if desired, may be substituted by any other of the many known types of such speed changing devices without affecting the invention proper.

It will also be understood that various other modifications, well known or conventional in the electronic arts, are readily applicable such as the substitution of a rectifier and filter for directcurrent power supply instead of the illustrated batteries, the substitution of transformers in place of the filament batteries shown, or the addition of further stages of amplification, as may be required.

While, in accordance with the foregoing, the substitution of any other source of energy for lamp 3, such as the provision of a transformer in place of battery 3, is possible, the use of a direct-current source such as battery 4, or the substitution of a rectified and well-filtered alternating-current power supply, offers certain advantages over the conventional alternating-current excitation of exciter lamp 3, especially when high-speed operation of web 1 is encountered. If lamp 3 is energized by alternating current, such as from the winding of a transformer, the intensity of light from lamp 3 will vary in the sinusoidal fashion of the alternating filament current of the lamp. As has been previously stated, the connections of the components with amplifier tubes Ai or A2 is such as to render the circuit responsive to a rapidly changing value of illumination falling upon the light sensitive cathodes 1 or I01. Hence, with exciter lamp 3 powered by the usual source of alternating current, the circuit is affected by the sinusoidal variation of the scanning beam intensity. The effect is detrimental to the maximum-obtainable sensitivity because of its obvious interference with the normal function of the change in beam intensity caused by the reference marks 2. This effect is completely eliminated when lamp 3 is energized from a direct-current source. Hence, the provision of a battery d or of equivalent rectified and filtered power at this particular place contributes to the sensitivity of the system and, therefore, affords an improvement over the conventional electronic circuits wherein the exciter lamp is powered from an alternating-current supply.

I claim as my invention:

1. Control apparatus for web speedregulation, comprising a single source of a directed beam of light disposed on one side of the web when in operation and directed toward the web to illuminate a scanning area thereon, a photoelectric device disposed on the web side of the light source for response to light from said source reflected from the scanning area, another photoelectric device disposed on the web side opposite the light source for response to light from said source passing through the scanning area, two amplifiers connected with said respective photoelectric devices and having respective utput circuits, and relay means having a control circuit, said two output circuits being connected with said control circuit and having, relative to said control circuit, the voltage polarity needed whereby a change in illumination of a given sense on either photoelectric device will produce a voltage change of a given sense in said control circuit.

2. Control apparatus for web speed regulation, comprising light source means for illuminating a web scanning area, two photoelectric devices disposed for response to light from said source reflected from and transmitted through, respectively, said area, said two devices having respective amplifying means each having an output circuit and resistance means in said output circuit, a relay means having a trigger circuit comprising a resistor and responsive to voltage impressed across said resistor, a capacitor series connected with said resistor, said two output circuits having a point of potential in common with said trigger circuit and being connected in parallel relation to each other across said series-connection of said resistor and said capacitor, whereby said voltage is cumulatively controlled by said two devices.

3. In control apparatus for an electric device utilized in connection with apparatus operating to move a web of material longitudinally of itself, in combination, two photoelectric tubes disposed relative to each other to simultaneously respond to light reflected from and transmitted through the web respectively, two electronic amplifiers having respective grid circuits connected to said photoelectric tubes and each having an output circuit, each output circuit being equipped with a resistor so as to provide a variable voltage across said resistor under control by one of said respective photoelectric tubes, a coupling circuit connected with said two resistors for cumulatively combining said two voltages, an electronic relay tube having a plate circuit and having a control electrode connected to said coupling circuit for controlling said plate circuit in response to the cumulative effect of said voltages. and an electric device connected to the plate to be controlled by said relay tube.

4. In an electric control system for an electric device utilized in connection with apparatus operating to move a web of material longitudinally wse'egasi-s 0"! men, in combination, en "electric device, two

'p'hoteelee'tric tribes 'fiispos'ed relative to each ether to simultaneously-respond to light reflected from and --transmitted through the web respectively, two electronic amplifiers having respem in'g a load resistor, two coupling resistors having a common ter'mi-nal end having respective o ther terminals attached 41o said lead resistors, respectively, a capacitor, a. charging eirc'uit for said capacitor which 'includes another res'istdr in series with said capa'cifo'r and extends *through said common terminal and the load lresistbrs of said output circuits so as $0 "predueei'a'cross said other resistor '-a variable control voltage determined by the Joint 'cumu'lative effects *fdf said pliotoelectric tubes, 2am electronic relay mube 'h'av- 118 im; a. trigger *circuit 'comi'ectefi across said ether resistor to be subject "to 'sai'd control voltage, and controlling circuits for interconnecting said-elecme device to said relay tube.

"I. BENDZ.

REFERENCES CITED The following references are of record in the like "of this patent:

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